JPS6250407A - Soaking method for metallic plate - Google Patents

Abstract

PURPOSE:To improve the soaking of a metallic plate by disposing plural pieces of linear heaters in parallel, placing the metallic plate below the heaters and oscillating the heaters at a specific amplitude and oscillation frequency orthogonally with the axis thereof and parallel with the plane of the metallic plate. CONSTITUTION:Plural pieces of the linear IR heaters 2 are housed in a unit 3 in parallel and the metallic plate 1 is placed below the same. A crystal grain size measuring instrument 4 by X-rays is attached to the opposite side. The entire part of the unit 3 is oscillated in an arrow direction 5 within the pane parallel with the plane of the metallic plate and the metallic plate 1 is heated by the heaters 2. The amplitude l(mm) and oscillation frequency f(Hz) of the oscillation are so determined as to satisfy the respective equations 0.25 d<=l<=d (d is spacing mm between the IR heaters), 0.20<=f<=300<=l. The heating of the metallic plate with the high soaking characteristic is thereby executed and the various changes arising in the metallic plate 1 are simultaneously measured during heating.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is capable of uniformly heating a metal plate by unidirectionally heating a metal plate using a plurality of heaters, by vibrating one layer according to certain conditions. It relates to a method for improving.

(Conventional technology) In recent years, with the advancement of advanced industrial technology centered on the automatic mold manufacturing sector and the weak electrical sector, there has been a shift from these manufacturing industries that use iron to the material manufacturing industry centered on iron. For example, in the metal materials sector, there are demands for even higher strength and improved processing.

In order to improve such material quality, first, simulations of various conditions are performed through laboratory experiments, and optimal manufacturing conditions are determined. This also applies to metals. This laboratory experiment is very important, and it can be said that the quality of the product is determined by the accuracy of the laboratory experiment.

When it comes to metallic materials, temperature conditions are the determining factor for any material in laboratory experiments. Moreover, it is a well-known fact that by improving the uniform heating of the sample, it is possible to reduce variations in material test values and collect effective data.

Recently, equipment that can perform rapid heating and rapid cooling, such as continuous annealing lines, which are one of the steel plate production lines, has become commonplace, and it goes without saying that heating furnaces that can simulate rapid heating and rapid cooling can be used even in the laboratory. is becoming common.

Recently, using such experimental equipment, efforts have been made not only to investigate the material properties after the simulation is completed, but also to perform non-destructive testing using X-rays, magnetic lines of force, etc. during the simulation to correlate the material properties. For example, by measuring the amount of internal strain in the metal plate, changes in crystal grain size, degree of growth of texture, etc. during the simulation, it is possible to determine at what point during the simulation these factors that affect material properties begin to change. , basic information such as when the change ends can be obtained, and at the same time, knowledge useful for determining optimal conditions such as 'Jv reduction of heating time can be obtained.

From the above, as a heating experimental device for metal materials,
Ideally, the object to be heated should have good uniform heating, be capable of rapid heating and cooling, and be able to be fitted with non-destructive inspection equipment such as X-rays and lines of magnetic force.

Examples of experimental equipment capable of rapid heating and cooling include so-called infrared heating devices that have a large number of infrared heaters, and devices that conduct electrical heating by passing a high current through a metal plate. However, these devices generally have poor uniform heating of the heated object compared to siliconite furnaces and fluidized beds. The difference becomes larger.

To solve this problem, there is a method as disclosed in Japanese Patent Application Laid-Open No. 58-26482, in which infrared heaters are used to heat both sides of a metal plate, and the heaters are shifted by half a pitch to improve uniform heating. This method is based on double-sided heating, and there is no space to install a nondestructive inspection device that uses the X&9 described above and the magnetic field line sub.

In addition, in the case of i11″FL heating, the uniform heating at the center of the metal plate is relatively good, but the temperature at the joint between the metal plate and the electrode becomes extremely low. Measurements using measuring devices that use magnetic lines of force to flow through the body, such as measuring devices that use electromagnetic induction, have the disadvantage that they are noisy and cannot be used at all. [Problems to be solved by the invention] Unreleased 1! Il provides a method for heating a metal plate with high uniformity in a heating furnace configured to heat the metal plate only from one side and simultaneously measure various changes occurring within the metal plate during heating. It is considered as II.

[F-stage to solve problems]

The present invention has been made in view of the following circumstances. (1) An experimental apparatus for heating a metal plate is used in which a plurality of infrared heaters are arranged in a row above the metal plate.

(2) When heating a metal plate, the infrared heater is vibrated in a direction perpendicular to the axis of the infrared heater and in a plane that runs along the surface of the metal plate.

Q) Vibrate so that the vibration amplitude 4cu (mm) and frequency f (Hz) satisfy the following (D formula, ■ formula).

0, 25 d≦l≦d...self...(1) i(1
and d: Infrared heater interval (mm) 0.20≦f≦30
0/Tachi...■ [Effect] Hereinafter, the present invention will be explained in more detail along with its effects.

FIG. 1 shows an example of the configuration of an experimental apparatus according to the present invention. In FIG. 1, a metal plate 1 is heated on one side by an infrared heater 2, and this infrared heater is housed in a unit 3, and this entire unit is moved left and right in the direction of arrow 5 in FIG. It has a mechanism that can vibrate at an amplitude (mm) and a frequency f□(z). In addition, the metal plate 1 is sandwiched between the infrared heater 2 and the crystal grain size measuring wave 'r' on the side opposite to the infrared heater 2.
i4 is the installation. In FIG. 1, the infrared rays emitted from the infrared heater 2 are uniformly irradiated onto the metal plate IL, and the scorching of the metal plate I is improved only when the vibration conditions of the infrared heater unit 3 are within a certain range. .

Next, we will specifically describe the research conducted by the present inventors using the apparatus shown in FIG.
The vibration @l (mm) and soaking of the metal plate 1 were investigated. With the heater unit 3 stationary, thermocouples were attached directly below the infrared heater 2 and on the metal plate surface between the heaters, and the temperature differences were compared while gradually increasing the amplitude. The results are shown in FIG.

In Figure 2, the vertical axis is the temperature difference between the two thermocouples, and the horizontal axis is the ratio of the amplitude to the heater pressure gld (mm) r = l
/d is shown in the figure. From FIG. 2, it can be seen that r≧0.25 is required to obtain uniform heating within 10°C. 5
In order to obtain uniform heating within °C, r≧0.40 is required. Moreover, when r exceeds 1, it means that the heater interval d is vibrated by 1, and there is no beneficial effect. Based on this result, the amplitude statement of the heater was determined as shown in equation 0.

0, 25 d≦text≦d (1) Furthermore, the present inventors investigated the relationship between the frequency f of the infrared heater 2 and the scorching heat of the metal plate l. A pair of thermocouples was attached on the metal plate 1 to examine changes over time. As a result, it was found that when the vibration applied to the infrared heater has a very low frequency, the thermocouple temperature oscillates at the same frequency as the vibration of the infrared heater, as shown in FIG.

The lower the frequency, the larger the amplitude of this thermocouple temperature.This is because the vibration frequency is low, so if the thermocouple part is oscillating directly to the heater, it will be high temperature, but if it is between the heaters, the temperature will drop to 1 minute. This is because it gives you time to do so. It has been found that in order to keep the difference between the maximum and minimum temperature of the thermocouple within 10°C, it is necessary to set the frequency f of the common infrared heater to 0.20 Hz or more. Also, with this frequency position, when two wooden thermocouples were attached to the metal plate 1 in the same way as when determining the amplitude range of the infrared heater, it was found that 10
It was found that the temperature difference was within ℃.

However, it has been found that if f becomes too large, the uniform heating will deteriorate.According to the research conducted by the present inventors, f
It was found that when the temperature is large, the temperature between the heaters becomes higher than that directly below the heaters. This relationship is shown in FIG. 4(a). Further, FIG. 4(b) shows a schematic diagram of the difference in the frequency f of the temperature change of the metal plate.

In FIG. 4(a), the horizontal axis represents the ratio between the frequency f and the amplitude. In order to satisfy the temperature uniformity within 10° C. in FIG. 4(a), the following equation 0 is required.

fX sentence≦300... ■This phenomenon occurs because when heating is performed at a high frequency f, there is a difference in the heater movement speed between the center position and both ends of the heater vibration. In other words, the heater moves quickly at the center of vibration, and the time it takes to heat the metal plate directly below it is short. However, the closer you get to both ends of the vibration, the slower the heater moves, and the area directly below it is exposed to infrared rays. As the time becomes longer, a temperature difference as shown by the broken line in FIG. 4(b) eventually occurs. Since this phenomenon is related to the moving speed of the heater, it is of course also related to the heater moving amplitude, and the larger the amplitude, the larger the temperature difference.

Based on the above, the range of the infrared heater frequency f is determined by the following two
It was established as a formula.

0.20≦f≦300/l... By satisfying the condition of 0 or more, it is possible to conduct experiments while improving the scorching heat of the metal plate that is the object to be heated. It is also possible to improve uniform heating by changing the vibration conditions of the infrared heater to the vibration conditions of the metal plate and vibrating the metal plate directly in the axial direction of the infrared heater. However, with the method of vibrating the metal plate, there is a large amount of noise in the measurement accuracy of the non-destructive inspection equipment or crystal grain size measuring device 4 using X-rays or magnetic field lines placed on the opposite side of the infrared heater across the metal plate 1 in Fig. 1. occurs, making measurement virtually impossible.

' 〔Example〕 Next, embodiments of the present invention will be specifically described.

As an example, an annealing experiment of a cold-rolled steel plate was conducted using the infrared heater furnace shown in FIG.

The purpose of this experiment was to collect basic data for material control using an austenite (hereinafter referred to as γ) phase fraction measuring device.

At 4 in FIG. 1, a gamma phase fraction measuring device using magnetic lines of force was installed. What is the chemical composition of the cold-rolled steel sheet used in the examples?

C: 0.075 ton 41% Si: 0.07 Heart % Mn: 1.48 Fee% P: 0.90 Hair t% S: 0.005% overlap A love: 0.040 mass% It is. Further, the annealing heat cycle is shown in FIG.

The purpose of the wood experiment was to obtain a tensile strength of 1 [60
So-called ferrite with ~62kgf/mrn'
The objective is to determine whether or not a martensitic composite structure high-strength steel sheet can be manufactured while controlling the γ phase fraction using the γ phase fraction measuring device 4 in FIG. In other words, in a continuous annealing line for cold-rolled steel sheets, Si, Mn,
When steel containing P or the like is annealed, an ugly film called temper color occurs on the steel plate, and the radial side heating that is generally carried out in a continuous annealing line becomes completely useless.

This is because the accurate emissivity is not constant because of the temper color of the steel plate. Such a situation cannot be resolved even if the inside of the continuous annealing furnace is made into a non-oxidizing atmosphere or a reducing atmosphere. Therefore, in the past, manufacturing of such composite structure high-strength steel sheets was carried out based on the experience of production line operators, and the quality of the manufactured products varied greatly and reliability was low. Therefore, as an alternative to this radiation temperature measurement, attempts have recently been made to control the material quality using a gamma phase fraction measuring device that uses magnetic lines of force. In other words, when manufacturing a high-strength steel sheet with a composite structure, it is rapidly cooled from a ferrite and γ2 phase state to a ferrite-bainite or ferrite-martensite two-phase structure at high temperatures.
By measuring the γ phase fraction before quenching, it is possible to predict the amount of bainite or martensite after quenching.

Specifically, a cold-rolled steel sheet having the composition L is annealed according to the annealing heat cycle shown in FIG. 5, the γ phase fraction at point A in FIG. 5 is measured, and the target material quality ( Determine whether a tensile strength of 60 to 62 kg f/mm') can be obtained.

A cold rolled steel sheet with the above composition has a tensile strength of 60 to 62 kgf/mI.
In order to satisfy T+', the martensite fraction after annealing is required to be 18 to 22%, and therefore, the temperature at 50°C/
It has been found that the γ phase fraction needs to be between 21 and 24% before quenching the S.

Using the gamma phase fraction measuring device 4 in Figure 1, when the gamma phase fraction reaches 21 to 24% of the range shown in Figure 1, start rapid cooling, and then measure the tensile strength by a tensile test.6 Experiment The following shows the case where the annealing furnace shown in FIG. The test was carried out twice without vibrating the heater part at all as shown in Figure 6.Then, tensile test pieces were cut out from the annealed cold-rolled sheet according to the test piece cutting procedure shown in Figure 6, and the tensile strength was investigated.

In FIG. 6, 1 is an annealed cold-rolled steel plate, A-F is a tensile test piece, and broken line 6 corresponds to the position of the infrared heater when the infrared heater is not vibrated. Figure 6(b) shows the sixth
It is a side view of figure (a).

The results of the tensile strength investigation are shown in FIG. In FIG. 7, the horizontal axis corresponds to tensile test piece symbols A-F in FIG. Moreover, the materials indicated by white circles in the figure are materials processed by the annealing method according to the present invention, and the materials indicated by black circles are materials processed by the conventional annealing method.

From Figure 7, book 9. In the conventional method, the tensile strength is all within the range of 60 to 62 kgf/mrn', whereas in the conventional method, the tensile strength varies widely. is high, and the tensile strength of the test piece between the infrared heater phases W is low. This is because the temperature directly below the infrared heater is high, and the γ phase fraction is correspondingly high, so after quenching, the martensite fraction increases and the tensile strength decreases. Due to the rise. Infrared heater phase again! The opposite is true for R, and after quenching, the martensor fraction is low and the tensile strength is low.

This result occurs because the gamma phase fraction measuring device senses the modulus information in a wide range of the steel plate. Therefore, even if the γ phase fraction before quenching is 21 to 24% according to the γ phase fraction measuring device,
When a steel plate is partially observed, the γ phase fraction does not look like -.

〔Effect of the invention〕

In the conventional method, the uniform heating of the metal plate is poor, making it impossible to accurately simulate an actual manufacturing line.

On the other hand, according to the present invention, when heating a metal plate on one side using an infrared heater, it is possible to improve the uniform heating of the metal plate, so that there is less variation in tensile strength and accurate measurement is possible. .

According to the present invention, when heating a metal plate on one side using an infrared heater, it is possible to improve uniform heating of the metal plate.

[Brief explanation of drawings]

Fig. 0'51 is a sectional view of a main part of an example of a metal plate single-sided heating device using an infrared heater for carrying out the method of the present invention, Fig. 2 is a graph showing the relationship between the amplitude of the infrared heater and uniform heating, and Fig. 3
Figure 4 is a graph showing the relationship between the frequency of the infrared heater and scorching heat, Figure 5 is an annealing heat cycle diagram used in the example, and Figure 6 is an Itadori diagram showing the procedure for collecting tensile test pieces after annealing.
FIG. 7 is a graph showing the tensile test results of test pieces obtained by the method of the present invention and the conventional method. l...Metal plate 2...Infrared heater 3...Heater unit

Claims (1)

[Claims] 1. To heat a metal plate, a plurality of linear heaters are arranged in parallel, a metal plate is placed below the heaters, and the heaters are placed in a direction perpendicular to the axis of the heater and in a direction perpendicular to the axis of the metal plate. vibrate in a plane parallel to the plane, and the amplitude of the vibration l
A method for soaking a metal plate, characterized in that (mm) and frequency f (Hz) are set to satisfy equations (1) and (2), respectively. 0.25d≦l≦d...(1) However, d: Infrared heater interval (mm) 0.20≦f≦300/l...(2)